摘要：Summary. Excess exposure to the metalloid selenium (Se), a trace element with both toxicological
and nutritional properties, has been implicated in the etiology of a human motor neuron disease
of unknown origin and extremely severe prognosis, sporadic amyotrophic lateral sclerosis (ALS).
This relation has been suggested on the basis of two epidemiologic investigations which found an
increased risk of ALS associated with residence in a seleniferous area or with consumption of drinking
water with unusually high levels of inorganic hexavalent Se, in South Dakota and in northern
Italy respectively. Biological plausibility to a Se-ALS relation is provided by veterinary medicine
observations and toxicological studies, showing that Se, particularly the inorganic forms, has a selective
toxicity to motor neurons in swine and in cattle. Neurotoxic effects of Se species have also been
demonstrated in laboratory studies and, for the inorganic forms, even at very low concentrations.
Selenium has also been shown to affect muscle function in experimental animal models. Overall,
these findings from the epidemiologic and the toxicological literature indicate that environmental Se,
particularly in its inorganic forms and at unexpectedly low levels of exposure, might be a risk factor
for ALS, suggesting the opportunity to further investigate this issue.
